MOLECULAR MARKERS AND GROUPING OF PARENTS IN MAIZE BREEDING PROGRAMS

In maize (Zea mays L.) breeding programs identifying potentially high yielding hybrids, assigning new inbreds to heterotic groups, and determining the parental line in a hybrid to which a potential donor line is most closely related, are significant problems. Data from a diallel cross among 14 maize inbreds were analyzed to evaluate use of molecular marker date to (i) predict yield potential of hybrids, (ii) assign inbreds to heterotic groups, and (iii) determine to which of the two inbred parents of a single cross a donor line is most closely related. Four of the inbreds were from Iowa Stiff Stalk Synthetic background, five were from a Lancaster Sure Crop background and five were unrelated to either Stiff Stalk Synthetic or Lancaster Sure Crop. Allozyme genotypes at 14 loci and restriction fragment length polymorphism (RFLP) variant types for 52 cDNA clones were obtained for the 14 inbreds. Modified Roger's distance (MRD) values (a measure of genetic distance between inbreds based on marker data) were not significantly correlated with hybrid yields; however, a hybrid value based on the number of marker loci having the highest yielding genotype was significantly correlated with hybrid yield. Cluster analysis based on MRD values agreed well with pedigree information, but did not always agree with groupings based on yield. Where parents of hybrids were distantly related, a measure of relative relationship based on proportion of homomorphic marker loci was significantly correlated with a measure of relationship based on yield. Where parents of a hybrid were more closely related, however, such correlations were low.